[PATCH 3.16.y-ckt 106/180] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[Luis Henriques]

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Vasily Averin <vvs at virtuozzo.com>

commit 01b9b0b28626db4a47d7f48744d70abca9914ef1 upstream.

In some cases tmp_bug can be not filled in cifs_filldir and stay uninitialized,
therefore its printk with "%s" modifier can leak content of kernelspace memory.
If old content of this buffer does not contain '\0' access bejond end of
allocated object can crash the host.

Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
Signed-off-by: Steve French <sfrench at localhost.localdomain>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/cifs/readdir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index b334a89d6a66..1320d1ecc630 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -849,6 +849,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 		 * if buggy server returns . and .. late do we want to
 		 * check for that here?
 		 */
+		*tmp_buf = 0;
 		rc = cifs_filldir(current_entry, file, ctx,
 				  tmp_buf, max_len);
 		if (rc) {